Re: Interfaces vs ZCA concepts
Tres Seaver <[email protected]>
| Newsgroups | gmane.comp.web.zope.devel |
|---|---|
| Message-ID | <[email protected]> |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Thomas Lotze wrote: > Martijn Faassen wrote: > >> Hey, >> >> Tres Seaver wrote: >> [snip] >>> Any code today which wants a utility is calling 'getUtilty' (if it >>> *knows* the utility must be registered) or 'queryUtility' (if it thinks >>> it might not be). Less facetiously than my first challenge: please >>> point to actual code in the wild which looks like:: >>> >>> try: >>> foo = getUtilty(IFoo, name='bar') >>> except ComponentLookupError: >>> # do something >>> >>> instead of:: >>> >>> foo = queryUtility(IFoo, name='bar') >>> if foo is None: >>> # do something >>> >>> I will argue that any code doing the first, outside of maybe tests of >>> the ZCA itself is plain broken. >> I have code like that in the wild - I have no real reason why I didn't >> queryUtility, but I didn't think it mattered. >> >> Why is it plain broken? Isn't getUtility supported to raise >> ComponentLookupError if it cannot find the required utility? > > The interface declaration for the zope.component API does assert that > getUtility raises a CLE if it cannot find the utility. Also, I wouldn't > say that queryUtility should be used instead of using getUtility and > catching the CLE, as that would deprive us of all the advantages of using > exceptions, such as propagation along the call stack. Those advantages don't obtain if the call site itself catches the CLE: at that point, all you have is a more expensive and less clear way to get what 'queryUtility' gives you. Tres - -- =================================================================== Tres Seaver +1 540-429-0999 [email protected] Palladion Software "Excellence by Design" http://palladion.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAksrvvwACgkQ+gerLs4ltQ64JgCfc9sKxivpsIZJT8A3ep+pW0cZ J7AAn0yRW2137WO7cHq92zAXCTj33cwf =anzG -----END PGP SIGNATURE----- _______________________________________________ Zope-Dev maillist - [email protected] https://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - https://mail.zope.org/mailman/listinfo/zope-announce https://mail.zope.org/mailman/listinfo/zope )